The present invention relates to the field of automated inspection systems for measuring the shape and configuration of manufactured parts.
The reconstruction of 3-dimensional surfaces has been attempted by employing interferometers for quantifying the surface characteristics of various objects. Other complex techniques employ moire contouring; see U.S. Pat. No. 3,943,278 to Ramsey. A summary of these techniques may be found in columns 1 and 2 of U.S. Pat. No. 4,525,858 to Kline et al.
Single solid state cameras employed in 3-dimensional object measurement tasks have also been deployed to record the surface reflections resulting from structured light sources, e.g. a plane fan of laser light, thereby to reconstruct height profiles over the surface; this approach requires relative motion between the part being measured and the measurement apparatus. Techniques employing laser triangulation and ultrasonic ranging, are also known, and are slow.
U.S. Pat. No. 4,070,683 to Altchuler et al. illustrates a technique employing a single camera for viewing an object having an optical grid pattern directed thereon. Distortions in the grid pattern are measured to determine the shape of the surface of the object. In U.S. Pat. No. 3,894,802, line patterns are also employed, which function in the manner of a range finder, whereby the changes in the shape of the object are indicated by various degrees of separation between the lines projected upon the object. A significant problem with the latter two patents is that the use of optically projected lines for determining shape would interfere with a simultaneous process of automatic edge detection, where not only the shape of a continuous surface of the part is to be measured, but the placement of edges are also to be automatically determined. Confusion between the lines utilized to measure the shape of the object with lines representing actual edges of a machined part, for example, renders the automatic processing of data derived from scanning the object quite difficult.